Apparently that happens to some 3DS', but it's only some defective ones, not all of them. He should exchange it, but he already has a lot of data on it, which he doesn't want to lose, so he has a lose/partially lose situation.
My brother's 3DS has a problem, area around the bottom screen, the analog stick, and the the start/select buttons are etching marks into the top screen. It's not supposed to do that.